title: Anti-activator QslA defines the quorum sensing threshold and response in Pseudomonas aeruginosa.
abstract: Quorum sensing (QS) in a bacterial population is activated when extracellular concentration of QS signal reaches a threshold, but how this threshold is determined remains largely unknown. In this study, we report the identification and characterization of a novel anti-activator encoded by qslA in Pseudomonas aeruginosa. The null mutation of qslA elevated AHL-dependent QS and PQS signalling, increased the expression of QS-dependent genes, and enhanced the virulence factor production and pathogenicity. We further present evidence that modulation of QS by QslA is due to protein-protein interaction with LasR, which prevents LasR from binding to its target promoter. QslA also influences the threshold concentration of QS signal needed for QS activation; in the absence of qslA, QS is activated by nine times less N-3-oxo-dodecanoyl-homoserine lactone (3-oxo-C12-HSL) than that in wild type. The findings from this study depict a new mechanism that governs the QS threshold in P. aeruginosa.
authors.affiliation: Institute of Molecular and Cell Biology, 61 Biopolis Drive, Proteos, Singapore.
authors.forename: Qihui
authors.initials: Q
authors.lastname: Seet
authors.forename: Lian-Hui
authors.initials: LH
authors.lastname: Zhang
mesh_terms: D054742:Acyl-Butyrolactones / Q000378:metabolism; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D015153:Blotting, Western; D015964:Gene Expression Regulation, Bacterial; D006714:Homoserine / Q000031:analogs & derivatives / Q000378:metabolism; D047468:Immunoprecipitation; D007783:Lactones / Q000378:metabolism; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D011552:Pseudomonas Infections / Q000235:genetics / Q000382:microbiology; D011550:Pseudomonas aeruginosa / Q000235:genetics / Q000378:metabolism / Q000472:pathogenicity; D053038:Quorum Sensing / Q000235:genetics* / Q000502:physiology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017422:Sequence Analysis, DNA; D015398:Signal Transduction / Q000235:genetics; D015534:Trans-Activators; D037521:Virulence Factors / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*
chemical_list: D054742:Acyl-Butyrolactones; D001426:Bacterial Proteins; D007783:Lactones; C080365:LasR protein, Pseudomonas aeruginosa; D015534:Trans-Activators; D037521:Virulence Factors; C085113:Pseudomonas aeruginosa autoinducer; D006714:Homoserine